It's my opinion that at this point, it may very well be that pollsters DO NOT want Biden replaced in the coming election, and releasing a poll that shows Biden is improving against Trump will lessen the calls from within his own party to dump his senile ***!
All too often, we have found that pollsters would rather DIRECT public opinion where they want it, rather than REFLECT the actual views of the country. It's not a very difficult thing to do to "guide" those polls where they want them to go, according to their agenda. And it WILL change as Election day draws nearer and those pollsters become concerned with their own reliability and accuracy.